1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing an insulated gate field effect transistor having a refractory metal silicide layer.
2. Description of the Related Art
Accompanied with the trend for higher integration of semiconductor devices, the device size has become increasingly fine. However, in the fine patterning of the insulated gate field effect transistor (hereinafter, referred to as MOS transistor), it is generally known that the short channel effect will create a problem. As a method for suppressing the short channel effect, it has been researched to make shallow the depth of the source/drain diffusion layer of the MOS transistor.
However, to simply make shallow the diffusion layer leaves problems such as increase of the sheet resistance and increase of the contact resistance with wiring materials. To overcome these problems, proposals to form elevated structures have been made, i.e., a structure that a silicon layer is selectively grown so as to selectively pile up on the diffusion layer and gate electrode, and a method that forms a metal silicide film on the foregoing piled up structure, as disclosed in the Japanese Patent Application Laid Open No. 2-288236.
As shown in FIG. 3(a), a device isolation oxide film 2 is formed on a surface of an N-type silicon substrate 1 to partition a device forming region. On the surface of the device forming region, a gate electrode 3 is formed, a gate electrode 4 of a silicon is formed, an insulating spacer 6 is formed, BF.sub.2 ions are implanted, and an annealing is applied, thus forming P-type diffusion layers 5-1, 5-2. Next, in order to expose a surface of the gate electrode 4 and surfaces of the P-type diffusion layers 5-1, 5-2, the surfaces are treated by a dilute HF. Thereafter, to remove a native oxide film, the silicon substrate is heated in a hydrogen atmosphere inside the growth chamber, or under a high vacuum and more than 800.degree. C., usually about 900.degree. C. And then, silicon layers 7-1, 7-2, 7-3 are grown by the selective CVD, using a silane system gas. Next, as shown in FIG. 3(b), a titanium film 8 is deposited on the whole surface, and an annealing under about 650.degree. C. is applied in an N.sub.2 atmosphere to form titanium silicide layers 9-1, 9-2, 9-3 as shown in FIG. 3(c). Next, a titanium film 8a remaining unreacted is removed.
According to the foregoing conventional method, it is possible to lower a resistance of the source/drain region having a shallow diffusion layer. However, to remove the native oxide film requires a high temperature heat treatment, which causes rediffusion of impurities. Therefore, although it is possible to make a diffusion layer as shallow as a diffusion layer of a MOS transistor having the gate length of about 0.5 .mu.m, it is impossible to apply the conventional method to a MOS transistor having a fine structure of deep submicron level.
In order to lower the threshold temperature for the preliminary treatment that enables to remove the native oxide film and to selectively grow the silicon layer, attempts in laboratories have been made, such as a method to use fluorine or hydrogen radical, and a method to irradiate ultraviolet rays in a hydrogen atmosphere; however, these methods are not established yet as a technique for mass production. The foregoing Japanese Patent Application Laid Open No. 2-288236 discloses a method to prevent the formation of the native oxide film in the atmosphere by using a CHF.sub.3 being a gas for etching in forming the insulating spacer to deposit a polymer containing a carbon on the surface of the silicon layer. However, the silicon layer is selectively grown at 900.degree. C. in that case, and it is not clear whether or not the method can prevent the formation of the native oxide film to the extent that a high temperature heat treatment becomes needless. Further, the carbon will increase a leakage current across the PN junction between the diffusion layer and the substrate, which is disadvantageous.
All in all, naturally a technique is preferable which lowers a resistance of the source/drain region without specially needing a high temperature heat treatment for removing the native oxide film.